Design consideration on ex-vessel neutron yield monitor for ITER

Summary form only given, as follows. Neutron yield measurement is one of the most important plasma diagnostic system in DD and/or DT fusion experiments and allows an absolute measure of the fusion power. In ITER experiments, main characteristics required for the neutron yield monitor are (1) real-time measurement (1ms time resolution), (2) stable and robust operation with high-reliability and redundancy in a hostile environment, (3) neutron-gamma rays discrimination characteristic, (4) wide dynamic range(from 8 to 11 orders of magnitude) and (5) appropriate detection efficiency characteristic for absolute measurement of total neutron yield, which means as a flat energy detector response as possible. To meet these requirements we propose a neutron yield monitor based on U-235 fission chambers with neutron moderators to be installed outside the vacuum vessel, which is routinely used at other tokamaks.